Hi Han, I have now created a task for adding the XYZ structure file reading support to relax (https://gna.org/task/index.php?7404). To start to implement this, I would suggest the following small steps: - First you already have a Gna! account (https://gna.org/users/han87), so creating this can be skipped. - Check out a fresh copy of the xyz branch of relax "svn co http://svn.gna.org/svn/relax/branches/xyz", or update an already checked out copy "svn up". - Find an XYZ file of a small organic molecule and attach it to the task. This is for the system test, to check that the data is correctly read. It should be relatively small so that the system test is quick, but complex enough to be a good test. Also tell me which directory it should be located in, and if I need to create directories in 'test_suite/shared_data' for it. - Create the system test by duplicating the code of 'test_read_pdb_internal1()' in the file 'test_suite/system_tests/structure.py'. Remember to keep the methods alphabetically ordered. Modify the code for the organic molecule. - Then run the test with: $ relax -s Structure.test_[han] replacing [han] with the name of the test. - Once the test is running (but it should be failing), then type: $ svn diff > diff and attach the diff file to the task. This would be a good start, and is how one should code. Once the system test passes, we will know that the XYZ reading is complete. If you have any questions, please don't hesitate to ask. Cheers, Edward